To many, "Max Angle" means 90 degrees.
To some, "Max Angle" means 89 degrees.
First of all, you are both wrong to apply the term "Maximum Angle" to a set angle. Why do you think things such as 720*, 360*, and 10105010* Degree turns exist? If you wanted to actually label an numeric value as maximum, you are now talking about an Infinite number. Meaning that a 90 Degree turn is nothing more, than a 90 degree turn. Not "Max Angle", unless you are naming the value of 90 to someone or something named Max in some relevance. - For this, you may as well call a 90 degree drift, a Kuroi Drift ;)
Secondly, to those of you who say the maximum angle is 89* degrees because that's how far your wheels will turn - this does not play any role in determining the angle of a CAR which is drifting. Since when was somebody's drift measured on the tire? You may as well use the TV Cameras to zoom in on the tire and watch the bloody piece of rubber slide on the corner, fuck the car. Somebody's Drifting Angle is measured on how far sideways the car has turned from it's original 0* degree position, to the beginning and centers of the apex. You could say:
"His entry angle was 95* degrees, mid point was 50* degrees and he exited with 5* degrees" - This explains the CARs angle at 3 points during a valid drift. If you would not consider angles over 90 degrees to be a drift, you may as well ban half the drivers from D1GP who have validly scored points by doing so.
Yes, the maximum angle your tires can turn is 89 degrees, but the question about drifting is: How far can your CAR turn sideways?
If drifting angle really was based on how far your tires could turn..and drifting is considered to be an art instead of a sport, what would happen if Di-Vinci turned his painting 180*'s around? Is it no longer a painting? Ask yourself that.